This invention relates generally to the treatment of spinal conditions, and more particularly, to the treatment of spinal stenosis using devices for implantation between adjacent spinous processes.
The clinical syndrome of neurogenic intermittent claudication due to lumbar spinal stenosis is a frequent source of pain in the lower back and extremities, leading to impaired walking, and causing other forms of disability in the elderly. Although the incidence and prevalence of symptomatic lumbar spinal stenosis have not been established, this condition is the most frequent indication of spinal surgery in patients older than 65 years of age.
Lumbar spinal stenosis is a condition of the spine characterized by a narrowing of the lumbar spinal canal. With spinal stenosis, the spinal canal narrows and pinches the spinal cord and nerves, causing pain in the back and legs. It is estimated that approximately 5 in 10,000 people develop lumbar spinal stenosis each year. For patients who seek the aid of a physician for back pain, approximately 12%-15% are diagnosed as having lumbar spinal stenosis.
Common treatments for lumbar spinal stenosis include physical therapy (including changes in posture), medication, and occasionally surgery. Changes in posture and physical therapy may be effective in flexing the spine to decompress and enlarge the space available to the spinal cord and nerves—thus relieving pressure on pinched nerves. Medications such as NSAIDS and other anti-inflammatory medications are often used to alleviate pain, although they are not typically effective at addressing spinal compression, which is the cause of the pain.
Surgical treatments are more aggressive than medication or physical therapy, and in appropriate cases surgery may be the best way to achieve lessening of the symptoms of lumbar spinal stenosis. The principal goal of surgery is to decompress the central spinal canal and the neural foramina, creating more space and eliminating pressure on the spinal nerve roots. The most common surgery for treatment of lumbar spinal stenosis is direct decompression via a laminectomy and partial facetectomy. In this procedure, the patient is given a general anesthesia as an incision is made in the patient to access the spine. The lamina of one or more vertebrae is removed to create more space for the nerves. The intervertebral disc may also be removed, and the adjacent vertebrae may be fused to strengthen the unstable segments. The success rate of decompressive laminectomy has been reported to be in excess of 65%. A significant reduction in the symptoms of lumbar spinal stenosis is also achieved in many of these cases.
More recently, a different surgical technique has been developed in which the vertebrae are distracted and an interspinous process spacer is implanted between adjacent spinous processes to maintain the desired separation between the segments. Currently, patient selection is based on history, physical examination, and imaging. These diagnostic modalities might be sensitive and specific to lumbar spinal stenosis, but they are limited in their ability to identify the proper interspinous process spacer candidate. Properly selecting the patients to receive an interspinous process spacer is important in assuring positive outcomes following implantation of the spacer.
It would thus be advantageous for a diagnostic device and procedure to be used to determine (i) whether an interspinous process spacer would provide relief for the patient, and (ii) the size of such a spacer that would be necessary to provide such relief. Such a diagnostic procedure could be performed in a doctor's office or other outpatient setting in addition to a standard hospital setting.